A. Technical Field
The present invention relates to a down-hole pump. More particularly, but not by way of limitation, this invention relates to a downhole draw-down pump used to withdraw fluid from a well bore and method.
B. Background Art
In the production of oil and gas, a well is drilled in order to intersect a hydrocarbon bearing deposit, as is well understood by those of ordinary skill in the art. The well may be of vertical, directional, or horizontal contour. Also, in the production of natural gas, including methane gas, from coal bed seams, a well bore is drilled through the coal bed seam, and methane is produced via the well bore.
Water encroachment with these natural gas and oil deposits is a well documented problem. Once water enters the well bore, production of the hydrocarbons can be severely hampered due to several reasons including the water's hydrostatic pressure effect on the in-situ reservoir pressure. Down hole pumps have been used in the past in order to draw down the water level. However, prior art pumps suffer from several problems that limit the prior art pump's usefulness. This is also true of well bores drilled through coal beds. For instance, in the production of methane from coal bed seams, a sump is often times drilled that extends past the natural gas deposit. Hence, water can enter into this sump. Water encroachment can continue into the well bore, and again the water's hydrostatic pressure effect on the in-situ coal seam pressure can cause termination of gas production. As those of ordinary skill will recognize, for efficient production, the water in the sump and well bore should be withdrawn, Also, rock, debris and formation fines can accumulate within this sump area and operators find it beneficial to withdraw the rock and debris.
Therefore, there is a need for a downhole draw-down pump that can be used to withdraw a fluid contained within a well bore that intersects a natural gas and oil deposit. These, and many other needs, will be met by the invention herein disclosed.